1. Field of the Invention
The present invention relates to the field of optical telecommunications. It relates in particular to an optical plug connector as claimed in the precharacterizing clause of claim 1.
2. Discussion of Related Art
Because of their wide bandwidth and insensitivity to electromagnetic interference fields, optical fiber networks are being used increasingly in all fields for data transmission. In this case, plug connectors are used for detachable connection between different cables and their cores, which plug connectors are arranged at the cable ends or core ends and, in the mated state, reliably input the light signals which emerge from the fiber ends on one side of the connector into the fiber ends on the other side of the connector.
As the complexity of transmission networks increases and the appliances that are used are increasingly miniaturized, the packing density of the plug connections is becoming ever more important. With standardized individual plugs of the LC, SC, ST type or the like, the achievable densities are essentially governed and limited by the comparatively large plug housings. A certain amount of compression can be achieved by the combination of individual plugs in pairs to form duplex plugs (see for example EP-A1-1 341 015). Other plug connector systems of the MT type admittedly achieve higher densities by using a common ferrule for a plurality of fibers, but they are restricted to optical cables in the form of ribbons, and are not suitable for the common plug connection between individual cores (see for example EP-A2-0 997 757 or WO-A1-2006098734).
In particular, plug connector systems such as these require direct contact between the end surfaces of the individual fibers which are fixed in the ferrules, and this necessitates accurate processing of the fiber ends which are flush with the ferrules, by various types of grinding processes, and precise orientation of the fiber ends during installation into the plug connectors and during mutual alignment in the inserted state.
On the other hand, it is known for optical means such as lenses to be used at the fiber ends in plug connector systems, in order to widen the beam emerging from the fiber ends and to make it parallel, thus making the requirements for mutual alignment of the fibers to be connected less stringent. Plug connector systems such as these are known for individual fibers, for example, from U.S. Pat. No. 5,768,458 A1 or for a plurality of fibers from JP-A-2007041222. It is also possible to use specially shaped mirror elements (DE-A1-100 43 985) instead of lenses.
However, with plug connector systems such as these, the fabrication of the fiber ends, as well as their alignment and fixing with respect to the beam-widening optical means or elements, are complex and problematic.